<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
</head>
<body>


<script>

    var obj = new Object();
    console.log(obj.aaa);
    obj.aaa = function () {
        alert(1);
    }
    console.log(obj.aaa);

    console.log(document["onclick"]);

    document.onclick = fn;

    function fn(){
        console.log(1);
    }

    console.log(document["onclick"]);

</script>
</body>
</html>